In our investigations concerned with the biochemical bases for the effects of environmental agents on animal behavior, we are focusing our attention on some of the consequences of modulation of gonadal steroid production in the neonate with respect to sexual differentiation in rodent (rat) brain. Monoamine oxidase (MAO) levels and turnover rates will be used as one criterion for reflection of sex steroid modulation, while other criteria will include estimations of serotonin and catecholamine levels and turnover rates in various parts of the brain. The results of these biochemical studies will be interpreted in the context of alterations in behaviors of the experimental animals.